Devoting time, energy, and money to non-profit pursuits in the general field of fantasy and fandom. It includes reading, collecting, corresponding, belonging to organizations, writing, publishing, recruiting new fans, visiting fellow-scientifictionists, perhaps living with them in a science fiction house, and attending fan gatherings. For membership in the FAPA, applicants must show "proof by credential of their interest in fantasyamateur activity, which shall consist of one of the following: (a) Contributions, in form of poetry, drawing, fiction, or non-fiction writing, published in two fantasyamateur publications not produced in the same city. (b) Position as editor or publisher of at least one issue of a fantasyamateur publication".

Most fen pass thru a certain cycle of activeness: After getting familiar with the field they start taking on projects right and left, not realizing that they're building up to a peak that they haven't time to maintain. Suddenly they announce that they must discontinue all fan activity, except maybe subscribing to one or two fanzines and keeping up with one or two correspondents, because activities of the outside world must take most of their time and energy. Some disappear from fandom at this point, but many others discover after a while that they still need the intellectual companionship and means of scifi expression in fandom and can find time to take on a little bit more activity and so at length find a fairly constant level that they can keep up, barring catastrophes like getting drafted, or married. (Not that there aren't quite a number of GI's and husbands keeping up a fair degree of activity).